Refractive overlays can be used in various ways to produce images of variable aspect. Lenticular lens arrays are a class of refractive array that most typically includes a set of lenses of cylindrical geometry arranged in a parallel manner. A specially prepared image may be fixedly mated to a lenticular array in such a way that that the image's aspect changes with a shift in the relative positions of the observer and the lenticular image. Alternately, separately mounted imagery may be displaced relative to a suitably positioned lenticular array so that a change in aspect is made visible to a stationary observer.
The modern practice of lenticular imaging has come to encompasses diverse transitions, including shifts of color, text, scale, and content as well as autostereoscopic and animation effects.
The special preparation of the image includes the step commonly known as interlacing. Interlacing combines image information from two or more images in a finely interleaved pattern that is coordinated with the pitch of the lenses. Interlacing in this manner briefly predates the invention of lenticular imaging, as it was initially proposed in 1896 by Auguste Berthier to promote a stereoscopic effect in conjunction with a parallax barrier screen.
A mechanically activated lenticular system is described in U.S. Pat. No. 592,631 to Hollander. In Hollander, the effects are limited to geometrical and chromatic patterns and does not expressly include any interlacing step. U.S. Pat. No. 624,042 to Jacobson describes the interlacing of right and left views. U.S. Pat. No. 624,043, also to Jacobson, combines this interlaced print with a corrugated transparent sheet to produce the first record of a lenticular “Stereograph”.
U.S. Pat. No. 1,150,374 to Kanolt recommends the use of many source images to produce a lenticular picture that simulates a continuous transition. The patent includes the fundamental calculations needed to properly compose such an image and locate such interposed multi-view imagery in optimal cooperation with a lenticular array.
Each of the U.S. Patents referenced herein is expressly incorporated by reference in its entirety.
Kanolt suggests various effects that may be obtained by this means, including an effect continuous motion. Kanolt also discloses that the method may equally be applied to convey temporal changes, such as an impression of growth of a plant or animal, or gradual shifts in the facial expression or facial features of a human subject.
The current core practice of preparing a lenticular image departs little in concept from Kanolt's descriptions from 1915, although the interlaced image in now principally composed using image processing software rather than earlier optomechanical methods.
Current lenticular software often includes options described by the terms 3D, flip, or zoom. A 3D image may be derived from a real scene, or synthesized from a layered image file composed in an image editing application. A lenticular image that exhibits an abrupt transition between images, whose subject matter may electively be related or unrelated, is known as a flip image. A zoom image is an image that shows a transition of text or image from one scale to another.
In the common understanding, a zoom image may be said to differ from the growth illusion described by Kanolt in that in a zoom image there is no representation of a passage of time. In a lenticular zoom image, a single source image is resampled at differing scales to ultimately draw attention to a particular area of the broader source image, much as a zoom lens would be used in videography.
Lenticular zoom images can vary in their composition or effect. For example, the zoom effect may be pervasive and continuous across the angular viewing range, or may be devised to occur only between two relatively static “zoomed out” and “zoomed in” phases. The zoom transition may be made to appear as a seamless radial blur, or may present a distinguishable set of progressively scaled versions of the source image.